Qualitative and quantitative analysis of wheat gluten proteins by liquid chromatography and electrospray mass spectrometry

Based on analysis by liquid chromatography/electrospray ionisation mass spectrometry, we have developed a new method for fast and sensitive fingerprinting of gliadins and glutenins in wheat flour. Using this procedure the two protein fractions from seven durum wheat varieties have been analysed by high resolution high performance liquid chromatographic separation coupled to accurate determination of molecular mass. In this way, the molecular mass of the single components from both gliadin and glutenin fractions were measured and more than forty components were detected for each fraction indicating a high heterogeneity. Although the chromatographic profiles were similar, the molecular masses of protein components with similar retention times among the varieties were often different. The difference ranged from a few mass units corresponding to single amino acid substitution(s) up to thousands implying peptide deletion or insertion along the protein chain. Two components representing about a half of the gliadin fraction, e.g. gamma(2)- and gamma(3)-gliadin, were identified through the N-terminal sequence and molecular mass determination. We suggest the use of the high level and the molecular mass of these gliadin components as markers to detect traces of wheat in gluten-free food preparations for celiac patients.